Power stop in response to overload



Aug. 5, 1969 F. H. CARY 3,460,018

POWER STOP IN RESPONSE TO OVERLOAD Filed on. 10.- 1966 INVENTOR FRANCIS H. CARY ATTORNEYS United States Patent US. Cl. 318-475 2 Claims ABSTRACT OF THE DISCLOSURE A motor driven actuator wherein the power means is made inoperative after the moved part has been brought into its desired position and wherein the actuator will cut off the power means not only at either end of the full stroke, but also during the stroke in either direction if any obstruction interferes with the normal motion of the moved part, and wherein the actuator has means which yields after the part has been brought into a desired position against the stop and the utilization of a single yieldable means permitting the power means to operate for a short period of time thereafter in either direction against the single yieldable means without placing an undue strain upon any of the parts and assuring that the part which has been moved will consistently be brought into its required position at either end of a stroke in opposite directions.

This invention relates to a power operated device which may be connected between a support and a member which is to be moved back and forth relative to said support between selected positions of operation and which may be operated to perform the function of moving some part positively and consistently into the positions which have been predetermined therefor. Although the invention is of general utility for the moving of mechanical parts, it is especially adapted for the movement of a valve from open to closed position.

The invention provides a device wherein a part may be moved forwardly and rearwardly between two positions predetermined by stops wherein the power means is deactuated after the moved part has reached either of the stops, there being incorporated therein a yieldable element which yields during the operation of the power means after the moved part has engaged either of the stops, in association with the control for the power means which operates after yielding of the yieldable means has occurred.

It is an object of this invention to provide a single yieldable means or unit which may be actuated in either direction; that is, it may be moved in one direction when one stop is engaged or may be moved in the other direction when the other stop is engaged, the arrangement being such that a duplication of yieldable means may be avoided.

Another object of this invention is to provide a motor driven actuator wherein the power means is made in operative after the moved part has been brought into its desired position and wherein the actuator has means which yields after the part has been brought into a desired position against the stop and the utilization of a single yieldable means permitting the power means to operate for a short period of time thereafter in either direction against the single yieldable means without placing an undue strain upon any of the parts and assuring that the part which has been moved will consistently be brought into its required position at either end of a stroke in opposite directions or at any desired intermediate position.

With reference to the drawings:

FIG. 1 is a schematic sectional view of my invention 3,460,018 Patented Aug. 5, 1969 employed for the opening and closing of a reciprocating valve;

FIG. 2 is a diagrammatic view of the circuitry involved for the control of the electric motor; and

FIGS. 3 and 4 are elevations of a fragmental portion of FIG. 1 showing closed and open positions of the valve.

In FIG. 1 of the drawings, a valve plug 10 is shown in a duct 11 with a valve stem 12 extending therefrom. The valve is illustrated in partly open position in full lines and in full open position in dotted lines when the valve stem is up. Closed position will be when the valve stem is down and the plug 10 closses the duct 11.

The valve stem 12 is connected to a first threaded member 15 by means of a collar 16 and set screw 17, the collar 16 being threaded into the internal threads of bore 18 in the first threaded member 15. This first threaded mem ber 15 is mounted so that it cannot rotate but may move axially of the bore 18. Its position may be indicated by arrow 19 movable along an indicator 20 which is fixed to a support 21 which in this case is one of the legs which supports the upper casing.

The valve stem extends thru a gland and bonnet 22 preventing fluid in conduit 11 from entering the operating parts of the apparatus and serving as a stop for the full open position of the plug 10 as shown in dotted lines. The closed position of the plug engaging seat 23 would serve as a stop for the closed position of the plug.

A second screw member 25 threadedly engages the first screw member 15 by reason of its external threads engaging the internal threads of member 15, and this second screw member is rotated by means of a gear 26 fixed on the second screw member or shaft 25 against axial movement along the shaft although the shaft while generally axially fixed is subject to slight movement axially thereof. The gear 26 is driven from a pinion 27 operated by electric motor 28 supported on a platform 29 mounted in casing 30 and is enclosed by a screw cover 31. Casing 30 is supported on the legs 21 heretofore mentioned. This casing is provided with a downwardly facing shoulder against which the flange 36- of the collar 37 engages. Collar 37 embraces a non-threaded portion 38 of the screw shaft 25. This collar is held against rotation with shaft 25 and is essentially slidable along the shaft portion 38. A thrust bearing 40 is engaged by a shoulder provided by the lower portion 41 of the hub of the gear 26 positioned between the collar 37 and the lower portion of this gear, while a snap ring 42 on the upper side of the gear hub holds the gear snugly against this bearing so there is no play between the gear and collar.

A nut 45 is fixed to the threaded portion 25 of the second screw member by a set screw 46 and provides an abutment shoulder 47 at its upper end upon which there is mounted a thrust bearing 48 to engage a second collar 49 surrounding the non-threaded portion 38 of the screw shaft and essentially slidable therealon g. These collars 37 and 49 are hold against rotation with the shaft and between these collars there is provided a resilient means consisting of concave and convex washers 50 oppositely positioned but which may be compressed and will at all times tend to spread the collars 3-7 and 49 along the shaft 38 against thrust bearings 40, 4'8 and against shoulders 41 and 47. These collars and resilient means 50 are contained within a depending housing and 56 extending downwardly from the lower portion of the casing 30, while a protective glove 57 extends from this housing to a first threaded or screw member 15 to porvide a clossure of some of the vital mechanism of the device.

The spindle 60 extends upwardly from the upper end of the screw shaft or second screw member 25 and is provided with a radially extending arm or disc 61 at its upper end, which projects between normally closed switches 62 and 63 as seen in FIG. 1 having plungers 64 and 65 on opposite sides of this radial arm 61.

If it is desired to move the valve stem 12 upwardly, switch 75 (FIG. 2) would be thrown downwardly to place motor 28 in circuit so as to rotate the shaft 25 in a direction to move the first threaded screw member 15 upwardly. When the first screw member has reached the limit of its upward motion by engagement of the valve plug with the valve bonnet, there would be a reaction by reason of this screw member not being able to move any further upwardly, and therefore there would be a tendency or movement of the shaft 25 downwardly, there being a compression of the resilient means 50 'by movement of this shaft downwardly and a pressure of the radial arm 61 on the plunger 65 as seen in FIG. 4 so as to open the circuit at 76 causing the motor to stop. If, however, it was desired that the valve stem 12 be moved downwardly, then the switch 75 would be thrown upwardly and a rotation of the screw 25 in a direction to move the first threaded member 15 downwardly. When the plug 10 engages the valve seat 23, it would be blocked from further movement, and consequently there would be a movement of the shaft 25 upwardly so as to force the plunger 64 upwardly as in FIG. 3 and open the switch at 77, thus stopping the motor 28.

The switches 76 and 77 will also operate to stop the motor if any obstruction interferes with the movement of the valve in any intermediate position between wide open and tightly closed.

In case the mechanism is used for some other operation than control of a valve, stop 70 may be used to have the same effect as the use of the bonnet 22 as a stop, and stop 71 may be used to have the same effect as the use of the valve seat 23 as a stop in conjunction with the traveling abutment 72 as above explained.

I claim:

1. In an actuator for moving a part to a prescribed position, a first screw member having connection to said part, a second screw member engaging the first screw member so that relative rotation of said screw members will produce operative movement of said first screw member, said second screw member provided with spaced opposed shoulders, means supporting said second screw member so that it may have rotary and axial movement, power means for rotating said second screw member, yieldable thrust means between and acting against said shoulders and resisting axial movement of said second screw member under normal load applied thereto, collars on said second screw member engaging said shoulders, said yieldable thrust means acting on said collars, said thrust means permitting axial movement of said second 1 screw member when an overload is applied thereto in either direction as a result of the said part reaching its prescribed position and means actuated by the axial movement of said second screw member to stop the operation of said power means.

2. In an actuator as in claim 1 wherein said collars are axially slidable and held against rotation with said second screw member.

References Cited UNITED STATES PATENTS 2,407,537 9/1946 Chapman 3l8475 X 2,517,373 8/1950 Ambrose 3l8475 3,171,292 3/ 1965 Wantland 318475 X 3,369,087 2/1968 Eller 318-475 X ORIS L. RADER, Primary Examiner L. L. HEWITT, Assistant Examiner US. Cl. X.R. 318-477 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 18 Dated August 5, 1969 Inventor) Francis H. Cary It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I- In the heading, Column 1, Line 4, after 02857 insert the following, -assignor to General Signal Corporation, a corporation of New York.

SIGRED AND SEALED FEB 2 41970 M Fletcher, 11'. mm m- JR- Oomlaaloaer at Patents Attesting Officer 

